Résumé : In order to evaluate the reproducibility of measurements of muscle capillary blood flow using the Xe133 method during an effort test on a conveyor belt, the authors analysed their results in 42 patients, carrying out two tests at an interval of 1 or 48 hr. The results obtained showed good correlation between the results of measurements carried out at an interval of 48 hr and a systematic bias between measurements carried out at an interval of 1 hr.